CN210800571U

CN210800571U - Two-degree-of-freedom adjusting device

Info

Publication number: CN210800571U
Application number: CN201921720657.XU
Authority: CN
Inventors: 薛靓; 李建钢; 赵雨; 胡常安; 田理; 罗舒桐
Original assignee: National Institute Of Measurement And Testing Technology Machinery Research Institute
Current assignee: National Institute Of Measurement And Testing Technology Machinery Research Institute
Priority date: 2019-10-14
Filing date: 2019-10-14
Publication date: 2020-06-19
Anticipated expiration: 2029-10-14

Abstract

The utility model provides a two degree of freedom adjusting device relates to precision measurement instrument technical field. The two-degree-of-freedom adjusting device comprises a top plate, a bottom plate and a supporting piece arranged between the top plate and the bottom plate, wherein the supporting piece is rotatably connected to the bottom plate and can rotate around a first axis perpendicular to the bottom plate, the top plate is rotatably connected to the supporting piece and can rotate around a second axis fixed relative to the supporting piece, and the first axis is not parallel to the second axis. The two-degree-of-freedom adjusting device is simple in structure and low in assembly cost.

Description

Two-degree-of-freedom adjusting device

Technical Field

The utility model relates to an accurate measuring instrument technical field particularly, relates to a two degree of freedom adjusting device.

Background

The two-degree-of-freedom adjusting device can be used for using or calibrating precision instruments such as an autocollimator and a laser range finder. The existing two-degree-of-freedom adjusting device needs to separately arrange a pitching rotating platform on a base and superpose a horizontal moving platform on the pitching rotating platform in order to realize platform pitching rotation and horizontal rotation, and has a complex structure and higher assembly cost.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a two degree of freedom adjusting device, its structure is succinct, and assembly cost is lower.

The embodiment of the utility model is realized like this:

an embodiment of the utility model provides a two degree of freedom adjusting device, including roof, bottom plate and the support piece that sets up between roof and bottom plate, support piece rotates to be connected in the bottom plate and can rotate around the first axis of perpendicular to bottom plate, and the roof rotates to be connected in support piece and can rotate around the second axis fixed for support piece, first axis and second axis nonparallel.

In an alternative embodiment, the first axis and the second axis are perpendicular to each other.

In an alternative embodiment, two connecting blocks are arranged at intervals on one side of the top plate close to the bottom plate along the extension direction of the second axis, the supporting piece is positioned between the two connecting blocks, and two ends of the supporting piece are respectively connected with the two connecting blocks in a rotating mode, so that the top plate can rotate around the second axis relative to the supporting piece.

In an alternative embodiment, the support member is rotatably connected to the base plate by a rotating member comprising a rotating post located between two connecting blocks, the rotating post being fixedly connected to the support member, the rotating post being rotatably connected to the base plate and being rotatable about the first axis relative to the base plate.

In an alternative embodiment, the rotation member includes a locking bolt, the rotation post is embedded in the base plate, and the locking bolt passes through the support member and is threadedly coupled with the rotation post to fix the rotation post to the support member.

In an alternative embodiment, the rotation post is provided with a first stop boss to prevent the rotation post from being separated from the bottom plate from a direction approaching the top plate.

In an optional embodiment, the two-degree-of-freedom adjusting device comprises a first adjusting assembly, the first adjusting assembly comprises a first adjusting rotating part, an adjusting block and a locking part, the adjusting block is connected to the top plate, the bottom plate is provided with a first sliding groove, the adjusting block is in sliding fit with the first sliding groove and can slide in the first sliding groove along a first preset direction, the first adjusting rotating part is in threaded fit with the adjusting block and penetrates out of the bottom plate to adjust the position of the adjusting block in the first sliding groove, and therefore the rotating angle of the top plate around the first axis is adjusted; the retaining member is connected to the bottom plate, and the retaining member is used for locking the position of regulating block in first spout.

In an alternative embodiment, the locking member includes a locking knob and a locking rod connected to the locking knob, a locking pad is disposed on a side of the locking knob facing the bottom plate, the locking rod extends into the first sliding groove and is in threaded connection with the adjusting block, and the locking pad is used for preventing the locking member from moving when the locking knob is screwed.

In an optional embodiment, the two-degree-of-freedom adjusting device includes a second adjusting assembly, the second adjusting assembly includes a second adjusting rotating member, the second adjusting rotating member penetrates through the top plate and is in threaded fit with the top plate so as to be capable of adjusting the angle of the top plate rotating around the second axis, a second sliding groove extending along a second preset direction is arranged at the top of the adjusting block, the second preset direction is perpendicular to the first preset direction, and the second adjusting rotating member is in sliding fit with the second sliding groove.

In an alternative embodiment, the second adjusting assembly includes a connecting member detachably connected to the bottom of the second adjusting rotary member, the connecting member is provided with a second stopping boss, the second stopping boss is in sliding fit with the second sliding groove, and the second stopping boss is used for preventing the second adjusting rotary member from being disconnected from the second sliding groove.

The utility model discloses beneficial effect includes:

the two-degree-of-freedom adjusting device comprises a top plate, a bottom plate and a supporting piece arranged between the top plate and the bottom plate, wherein the supporting piece is rotatably connected to the bottom plate and can rotate around a first axis perpendicular to the bottom plate, the top plate is rotatably connected to the supporting piece and can rotate around a second axis fixed relative to the supporting piece, and the first axis is not parallel to the second axis. Two degree of freedom adjusting device is through setting up support piece between roof and bottom plate to make support piece relative bottom plate rotate around the first axis of perpendicular to bottom plate, the roof can rotate around the second axis relative support piece, and because first axis and second axis nonparallel, this two degree of freedom adjusting device can make the roof realize rotating on two directions for the bottom plate with the help of support piece, with current stack on the base set up every single move rotary platform and horizontal motion platform and realize that the roof can carry out the pivoted adjusting device of two degrees of freedom for the base and compare, the structure is more succinct, assembly cost reduces.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of a first view angle of a two-degree-of-freedom adjusting device according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a second view angle of a two-degree-of-freedom adjustment apparatus according to an embodiment of the present invention;

fig. 3 is a cross-sectional view of a two-degree-of-freedom adjustment apparatus according to an embodiment of the present invention;

FIG. 4 is an exploded view of a rotating member according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a first adjusting assembly in an embodiment of the present invention;

FIG. 6 is a schematic structural view of a locking member according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a second adjusting assembly in an embodiment of the present invention;

fig. 8 is an exploded view of a second adjustment assembly in an embodiment of the present invention.

Icon: 100-two degree of freedom adjustment means; 110-a top plate; 112-connecting blocks; 120-a first axis; 122-second axis; 130-a backplane; 134-a first runner; 150-a support; 152-a rotating member; 153-locking bolts; 154-rotating cylinder; 156-a first stop boss; 157-cushion columns; 160-a first adjustment assembly; 162-a first adjustment swivel; 163-adjusting the spring; 164-a conditioning block; 165-a second runner; 166-a locking member; 167-locking knob; 168-a locking lever; 169-a locking pad; 170-a second adjustment assembly; 172-a second adjustment swivel; 174-a connector; 175-a second stop boss; 176-nut.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the position or positional relationship based on the position or positional relationship shown in the drawings, or the position or positional relationship which is usually placed when the product of the present invention is used, and are only for convenience of description and simplification of the description, but do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.

Furthermore, the terms "horizontal", "vertical" and the like do not imply that the components are required to be absolutely horizontal or pendant, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," and "connected" are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 1 and 2, the present embodiment provides a two-degree-of-freedom adjustment apparatus 100, which includes a top plate 110, a bottom plate 130, and a support 150 disposed between the top plate 110 and the bottom plate 130. The support 150 is rotatably connected to the base plate 130 and is capable of rotating about a first axis 120 perpendicular to the base plate 130, and the top plate 110 is rotatably connected to the support 150 and is capable of rotating about a second axis 122 fixed relative to the support 150, the first axis 120 being non-parallel to the second axis 122, such that the top plate 110 is capable of rotating in two directions relative to the base plate 130 via the support 150.

In the present embodiment, the first axis 120 and the second axis 122 are perpendicular to each other, and the second axis 122 is parallel to the bottom plate 130, so that when the bottom plate 130 is horizontally placed, the support 150 can horizontally rotate with respect to the bottom plate 130, the top plate 110 can pitch-rotate with respect to the support 150, and the top plate 110 can perform movements with two degrees of freedom of pitch-rotation and horizontal-rotation with respect to the bottom plate 130. In other embodiments, the second axis 122 may not be parallel to the bottom plate 130, i.e. the first axis 120 and the second axis 122 may not be perpendicular to each other, and it is only necessary to ensure that the second axis 122 and the first axis 120 have different directions, so that the top plate 110 can rotate with two different degrees of freedom.

The top plate 110 and the bottom plate 130 are rectangular plates, and one side of the top plate 110 is rotatably connected to the support 150. Specifically, two connection blocks 112 are arranged at intervals along the extending direction of the second axis 122 on one side of the top plate 110 close to the bottom plate 130, in the present embodiment, the two connection blocks 112 are detachably mounted on the bottom surface of the top plate 110 through screws, and in other embodiments, the connection blocks 112 may be integrally formed with the top plate 110.

The support 150 has a substantially rectangular parallelepiped shape, and a length direction of the support 150 is parallel to the second axis 122. The supporting member 150 is located between the two connecting blocks 112 and two ends of the supporting member 150 are respectively rotatably connected to the two connecting blocks 112, so that the top plate 110 can rotate around the second axis 122 relative to the supporting member 150. In this embodiment, the connecting blocks 112 and the supporting members 150 are rotatably connected by a rotating shaft, and two ends of the supporting members 150 are respectively in contact with the two connecting blocks 112 to prevent the top plate 110 from swinging relative to the supporting members 150, so that when the top plate 110 horizontally rotates relative to the bottom plate 130, the supporting members 150 are driven to horizontally rotate together.

Referring to fig. 3 and 4, the supporting member 150 is rotatably connected to the base plate 130 via a rotating member 152. The rotating member 152 includes a rotating column 154 located between the two connecting blocks 112, the rotating column 154 is fixedly connected to the supporting member 150, and the rotating column 154 is rotatably connected to the base plate 130 and can rotate around the first axis 120 relative to the base plate 130.

Specifically, for ease of assembly, the rotation member 152 includes a locking bolt 153, and the rotation post 154 is embedded in the base plate 130. The locking bolt 153 passes through the support member 150 and is threadedly coupled with the rotating post 154 to fix the rotating post 154 to the support member 150. The bottom plate 130 is provided with a reducing through hole, and the section of the reducing through hole is in an i shape, namely, the reducing through hole is composed of a first small-diameter section in the middle and first large-diameter sections at two ends. The rotating column 154 is vertically disposed in the reducing through hole, the rotating column 154 is provided with a first stopping boss 156 to prevent the rotating column 154 from being separated from the bottom plate 130 from a direction close to the top plate 110, the first stopping boss 156 is disposed at a position close to the bottom of the rotating column 154, and the first stopping boss 156 is stopped in a first large-diameter section at the lower end of the reducing through hole. A sinking groove is formed at the middle portion of the supporting member 150, and a locking bolt 153 is inserted through the supporting member 150 from the sinking groove to be threadedly coupled to a rotating post 154 embedded in the base plate 130 so as to tightly couple the supporting member 150 and the rotating post 154. Thus, when the top plate 110 rotates horizontally relative to the bottom plate 130, the support 150 drives the rotating column 154 to rotate horizontally relative to the bottom plate 130, that is, the first axis 120 is the central axis of the rotating column 154. To ensure the precision of the rotation adjustment, a damping material may be disposed on the surface of the rotating column 154 contacting the reducing through hole to control the friction force applied to the rotating column 154 during rotation, thereby facilitating fine adjustment. In other embodiments, the rotating column 154 can be directly fixedly connected to the bottom of the supporting member 150 and rotatably connected to the bottom plate 130, and only the assembly is required.

In this embodiment, in order to prevent the support member 150 from directly contacting the upper surface of the bottom plate 130 to affect the rotation adjustment, a pad column 157 is embedded in the first large diameter section at the upper end of the variable diameter through hole, and the pad column 157 supports the support member 150 and is relatively fixed to the support member 150. Specifically, the cushion column 157 includes a second small diameter section and a second large diameter section that are sequentially connected from top to bottom, the bottom of the second large diameter section is embedded in the variable diameter through hole, and the top of the second small diameter section is embedded in the bottom of the support member 150. The columns 157 lift the supporting member 150 upward so that the supporting member 150 does not directly contact the base plate 130. The locking bolt 153 extends downwardly from the support member 150 through the pad column 157 and is threadedly coupled to the rotation column 154, thereby locking the support member 150, the pad column 157, and the rotation column 154 together, such that when the top plate 110 is horizontally rotated about the first axis 120, the support member 150, the pad column 157, and the rotation column 154 are horizontally rotated together with respect to the bottom plate 130. The surface of the pad 157 that contacts the base plate 130 may also be provided with a corresponding damping material to ensure adjustment accuracy. It is understood that in other embodiments, the pad column 157 may not be provided, as long as the adjustment accuracy of the corresponding horizontal rotation can be achieved.

Referring to fig. 5, the two-degree-of-freedom adjustment apparatus 100 includes a first adjustment assembly 160, and the first adjustment assembly 160 includes a first adjustment rotating member 162, an adjustment block 164, and a locking member 166. The first adjustment rotating member 162 is a screw or a lead screw with a knob. The bottom plate 130 is provided with a first sliding chute 134, and the first sliding chute 134 is located at one end of the bottom plate 130 far away from the variable diameter through hole. The adjusting block 164 is slidably engaged with the first sliding groove 134 and can slide in the first sliding groove 134 along a first preset direction (shown as ab direction). In the present embodiment, the first predetermined direction is parallel to the extending direction of the second axis 122. The first adjustment rotating member 162 is fixed with respect to the base plate 130 in a first preset direction. The adjusting block 164 is connected to the top plate 110 at a position on the top plate 110 such that when the adjusting block 164 moves in the first sliding slot 134, the side of the top plate 110 away from the connecting block 112 is moved accordingly, thereby allowing the top plate 110 to rotate around the first axis 120. The first adjusting rotary member 162 passes through the bottom plate 130 to the first sliding groove 134 along the first preset direction, and the first adjusting rotary member 162 is in threaded fit with the adjusting block 164 and passes through the bottom plate 130 to adjust the position of the adjusting block 164 in the first sliding groove 134, so as to adjust the rotation angle of the top plate 110 around the first axis 120, that is, the horizontal rotation angle of the top plate 110 is adjusted by adjusting the knob of the first adjusting rotary member 162 to adjust the displacement of the adjusting block 164. In this embodiment, the first adjusting rotary member 162 is sleeved with an adjusting spring 163 for eliminating the return gap. The adjustment spring 163 contacts the base plate 130 at one end and the adjustment block 164 at the other end.

Referring to fig. 6, the locking member 166 is connected to the base plate 130, and the locking member 166 is used for locking the position of the adjusting block 164 in the first sliding groove 134. In this embodiment, the locking member 166 includes a locking knob 167 and a locking bar 168 connected to the locking knob 167, a side of the locking knob 167 facing the bottom plate 130 is provided with a locking pad 169, and the locking bar 168 extends along a second predetermined direction (cd shown) perpendicular to the first predetermined direction. The first predetermined direction and the second predetermined direction are both perpendicular to the extending direction of the first axis 120. The locking bar 168 extends into the first sliding groove 134 and is threadedly engaged with the adjustment block 164, and the locking pad 169 is pressed between the locking knob 167 and the sidewall of the base plate 130 when the locking knob 167 is tightened, so as to prevent the locking member 166 from moving in the first predetermined direction by friction, thereby locking the position of the adjustment block 164 in the first sliding groove 134. In addition, when the position of the adjustment block 164 is adjusted, the locking bar 168 can be locked against rotation by mounting a set screw on the base plate 130.

Referring to fig. 7 and 8, the two-degree-of-freedom adjustment apparatus 100 includes a second adjustment assembly 170, the second adjustment assembly 170 includes a second adjustment rotating member 172, and the second adjustment rotating member 172 is a screw with a knob. The second adjustment rotating member 172 passes through the top plate 110 and is screw-engaged with the top plate 110 to enable adjustment of the angle of rotation of the top plate 110 about the second axis 122, i.e., adjustment of the pitch rotation angle of the top plate 110. The top of the adjusting block 164 is provided with a second sliding slot 165 extending along a second preset direction, and the second adjusting rotating member 172 is in sliding fit with the second sliding slot 165. When the top plate 110 horizontally rotates about the first axis 120, the second sliding groove 165 may allow the side of the top plate 110 away from the connection block 112 to move in the second predetermined direction to approach or separate from the support 150, avoiding interference with the horizontal rotation of the top plate 110.

In this embodiment, the second adjusting assembly 170 includes a connecting member 174 detachably coupled to the bottom of the second adjusting rotating member 172 to facilitate assembly. The connector 174 is cylindrical to avoid interfering with the rotational adjustment of the second adjustment assembly 170. The connecting member 174 is provided with a second stopping boss 175, the second stopping boss 175 is in sliding fit with the second sliding groove 165, and the second stopping boss 175 is used for preventing the second adjusting rotary member 172 from being disconnected from the second sliding groove 165. The second adjusting rotary member 172 may be sleeved with a nut 176 at a position above the top plate 110 to achieve vertical position limitation. In other embodiments, the second adjusting rotating member 172 can be directly slidably engaged with the second sliding groove 165 without the connecting member 174, and only the normal assembly is ensured.

The working principle and the working process of the two-degree-of-freedom adjusting device 100 are as follows:

when the bottom plate 130 is horizontally placed, the horizontal rotation angle of the top plate 110 is adjusted by the first adjusting assembly 160. Rotating the first adjusting rotating member 162 drives the adjusting block 164 to move in the first sliding slot 134 along a first predetermined direction (shown as direction ab), so as to drive the second adjusting assembly 170 to move, and further drive the top plate 110 to move correspondingly. Meanwhile, since the second adjusting assembly 170 is slidably connected to the second sliding slot 165 of the adjusting block 164, a side of the top plate 110 away from the connecting block 112 can be close to or away from the supporting member 150 along a second predetermined direction (cd direction shown), so as to ensure that the top plate 110 can normally horizontally rotate around the first axis 120, and the top plate 110 drives the supporting member 150 to rotate around the first axis 120 relative to the bottom plate 130. The second adjusting assembly 170 is threadedly engaged with the top plate 110, and both ends of the supporting member 150 are rotatably connected to the connecting blocks 112 of the top plate 110, so that the top plate 110 can be rotated about the second axis 122 relative to the bottom plate 130 by rotating the second adjusting assembly 170, i.e., the pitch rotation angle of the top plate 110 can be adjusted.

The two-degree-of-freedom adjustment apparatus 100 achieves adjustment of the top plate 110 with respect to the bottom plate 130 in two degrees of freedom by providing a support 150 rotatably connected to each of the top plate 110 and the bottom plate 130 between the two. The supporting member 150 can horizontally rotate around the first axis 120 relative to the bottom plate 130, and the top plate 110 can pitch and rotate around the second axis 122 relative to the supporting member 150, so that the two-degree-of-freedom adjusting device 100 has a simple structure and is low in assembly cost.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A two degree-of-freedom adjustment device comprising a top plate, a bottom plate, and a support disposed between the top plate and the bottom plate, the support being pivotally connected to the bottom plate and being capable of pivoting about a first axis perpendicular to the bottom plate, the top plate being pivotally connected to the support and being capable of pivoting about a second axis fixed relative to the support, the first axis being non-parallel to the second axis.

2. The two degree-of-freedom adjustment device of claim 1, wherein the first axis and the second axis are perpendicular to each other.

3. The two-degree-of-freedom adjustment device according to claim 1, wherein two connection blocks are provided at intervals along the extension direction of the second axis on one side of the top plate close to the bottom plate, the support member is located between the two connection blocks, and two ends of the support member are respectively rotatably connected to the two connection blocks, so that the top plate can rotate around the second axis relative to the support member.

4. The two degree-of-freedom adjustment device of claim 3, wherein the support member is rotatably coupled to the base plate via a rotating member, the rotating member including a rotating post located between the two connecting blocks, the rotating post being fixedly coupled to the support member, the rotating post being rotatably coupled to the base plate and being rotatable relative to the base plate about the first axis.

5. The two degree-of-freedom adjustment device of claim 4, wherein the rotation member includes a locking bolt, the rotation post is embedded in the base plate, and the locking bolt passes through the support member and is threadedly coupled with the rotation post to fix the rotation post to the support member.

6. The two degree-of-freedom adjustment device of claim 4, wherein the rotation post is provided with a first stop boss to prevent the rotation post from being disengaged from the base plate from a direction approaching the top plate.

7. The two degree-of-freedom adjustment device according to claim 1, comprising a first adjustment assembly including a first adjustment rotating member, an adjustment block and a locking member, wherein the adjustment block is connected to the top plate, the bottom plate is provided with a first sliding slot, the adjustment block is in sliding fit with the first sliding slot and can slide in the first sliding slot along a first preset direction, and the first adjustment rotating member is in threaded fit with the adjustment block and penetrates out of the bottom plate to be able to adjust the position of the adjustment block in the first sliding slot, thereby adjusting the angle of rotation of the top plate around the first axis; the retaining member is connected to the bottom plate, the retaining member is used for locking the position of regulating block in the first spout.

8. The two degree-of-freedom adjustment device according to claim 7, wherein the locking member includes a locking knob and a locking lever connected to the locking knob, a locking pad is provided on a side of the locking knob facing the base plate, the locking lever extends into the first sliding groove and is in threaded connection with the adjustment block, and the locking pad is used for preventing the locking member from moving when the locking knob is screwed.

9. The two degree-of-freedom adjustment device according to claim 7, comprising a second adjustment assembly including a second adjustment rotating member passing through and threadedly engaged with the top plate to enable adjustment of the angle of rotation of the top plate about the second axis, the top of the adjustment block being provided with a second sliding slot extending in a second predetermined direction perpendicular to the first predetermined direction, the second adjustment rotating member being slidably engaged with the second sliding slot.

10. The two degree-of-freedom adjustment device of claim 9, wherein the second adjustment assembly includes a connector detachably connected to a bottom of the second adjustment rotator, the connector being provided with a second stop boss slidably engaged with the second runner, the second stop boss being configured to prevent the second adjustment rotator from being disconnected from the second runner.